Friday, December 04, 2009

Arctic blast pushing into Prairies

Arctic air has finally moved into the Prairies, and an even colder surge of Arctic air will be pushing into the Prairies today through the weekend thanks to a strong area of high pressure building down from the Yukon. This second blast of Arctic air is currently pushing into Alberta with strong northerly winds, and snow and blowing snow giving near blizzard conditions through central and southern AB. This area of snow will push into the northern US, but the accompanying cold air will push across the eastern prairies over the weekend into early next week, bringing well below normal temperatures across southern MB. Look for highs in the minus teens by early next week with lows in the minus 25 to minus 30 range.

Prior to 1960, snowfall measurements were simply converted 10:1 for water equivalent. So snowfall (in cm) was always 10X the water equivalent (or the same value in cm as mm) I belive they started measuring actual water equivalent of snowfall back around 1960 or so. That continued until 2003 when they stopped taking snowfall measurements at the airport, and reported water equivalent values of the snow only.

So we went from snowfall amounts but no water equivalent readings from 1872 to 1960, to snowfall + water equivalent values from 1960-2003, to water equivalent but no snowfall amounts from 2003-present.

Not sure if that clears it up for you, or just makes the issue more confusing!

Quite the monster high pressure over the Yukon.. 1060 mb! Temperatures however not as cold as you would expect under such a massive high.. "only" in the mid minus 20s. If this was January or February, you'd be looking at -40 to -50C temperatures up there!

Given the lack of snow cover I believe the long range guidance is underestimating those high temperatures. As Rob mentioned, the source region for our airmass is not all that cold (all things considered) and the sparse snow cover will allow for moderation than normally would be the case.

With an ongoing moderate El Nino and limited snow pack I would not be surprised if we return to a near or above normal pattern faster than the models would suggest.